Additive drawing with grease pencil
I fixed it. This change works nicely!

def draw_multiple_circles_animated(gp_layer):
    gp_frame = gp_layer.frames.new(0)
    for frame in range(60):
        gp_layer.frames.copy(gp_frame)
        radius = sin(frame/30)
        draw_circle(gp_frame, (0, sin(frame/3 ), frame/3), radius, 80)